Patent GB-1003361-A (GB)
Title: Radio direction finding system with visual display
IPC: G01S3/14
Filed: 1961-10-23
Abstract: 1,003,361. Radio direction finding; aerials. M. WAECHTLER. Oct. 23, 1961 [Oct. 24, 1960], No. 37837/61. Headings HGA and H4D. A radio direction finder system comprises an array of similar unidirectional antennµ, arranged so that the main lobes of their respective horizontal polar diagrams radiate symmetrically outwards from points equally spaced around a circular arc, Figs. 2 and 3, or from a common centre, Figs. 1 and 4, and overlap such that the angle # between the axes of symmetry of adjacent lobes is equal to half the angular width of the lobe measured between directions of zero sensitivity such that a signal irrespective of its bearing is simultaneously received by two adjacent antennµ only, and a C.R.T. display apparatus comprising X and Y deflections amplifiers and feeder means coupling such antennµ independently to the X and Y amplifiers, the feeder means being such that, when in response to a signal an antenna generates a voltage u, a voltage equal to ku cos α is applied to the Y amplifier and a voltage equal to ku sin α is applied to the X amplifier, where k is a constant and α is the azimuth angle of the direction of maximum sensitivity of the antenna in question. In a modification a C.R.T. having a trace with an inclination variable over 180 degrees is provided with a corresponding cooperating measuring cursor, and feeder means, whereby the voltages applied to the K and Y amplifiers are ku cos #/# and ku sin α#/#, where # is   the angle over which the array is sensitive. A signal received on bearing p, Fig. 4, by antenna X generates a voltage u therein and this is passed to Y and X deflection amplifiers I and II, Fig. 2, through conductances g xa  and g xc  to produce voltages ku cos α x  and ku sin α x  at the respective deflection amplifier inputs. The conductances g xa  and g xc  may comprise transmission lines, capacitances, or the crossed pairs of plates of a capacitive goniometer. The signal is also received on an adjacent antenna (X+ 1) and the resulting voltage is passed as above to the Y and X amplifier inputs, respectively, multiplied by factors k cos α x+1  and k sin α x+1 . The outputs of the two amplifiers are applied respectively to the Y and X plates of the C.R.T. and produce a line trace having an inclination q given by:-   tan q = f(x) Sin α x +f(x+1) Sin αx+1/f(x) Cos α x +f(x+1) Cos α x+1  (1)   where f (X) and f (X+1) are the relative sensitivities of the two antennµ in the direction p. Since f(X)= 0 when p=α x+1  and f (X+1)=0 when p=αx and f(X)=f(X+1) when p= (α x +#/2), tan q=tan p, or q=p, when p=α x , α x +#/2 and α x+1 . However, the lobes are formed such that f(X) is proportional to sin (# - 0), where # is the angle between the radius vector of the lobe in the direction p, and the axis of symmetry of the lobe, so that equation (1) becomes tan q=tan p for all values of p. In order to determine the sense of the bearing indicated on the C.R.T. each deflection amplifier is provided with two independent inputs a and b, and c and d. The antennµ are connected to one or more of the inputs depending on their value for α, according to the following table. Such a system for 16 antennµ is shown in Fig. 3. Means are provided whereby selected pairs of the amplifier inputs may be earthed and the quadrant in which the signal is received is found from observing the inputs which, when earthed, causes no change in the C.R.T. trace. A table connecting these inputs with the corresponding quadrants is:- The antennµ may be dipole arrays, microwave horns or slot antennµ.